My wife had something similar. Her mother gained custody of her and took her from her father when she was very young. Her mother moved her to another state, changed her name and married the man who became her step dad. Mom and step dad then proceeded to lie and tell her horror stories for the next 30 years so she would never even want to meet him. Despite their best attempts, she still had a very strong curiosity about who he was and what had happened. Her aunt initiated contact with her mom, as they had been childhood friends. My wife then met her aunt for the first time in her life that she remembers. This led to meeting her father for the first time since she was about 3.
It turns out that he is a really nice guy, and part of a very kind and loving family. With the maneuvers that her mom pulled, he was without the ability to contact her and had regrettably given up. They started with a phone call, then when time allowed, we went to meet him. It was really important to go into it without any preconceived notions or expectations.
Since she has re-established contact and met him, she has achieved a level of peace with herself that had not previously been possible. With a better understanding of the situation from another viewpoint, she has been able to come to terms with some things that had been unresolved, as has her birth father.
Their relationship is ongoing, and has turned out pretty well. I know that this is not always the case though, which is why it was very important to not have any expectations of a result.